Motor

Abstract

A motor has a stator and a rotor that is formed of two rotor parts fitted on a rotor shaft in a fashion preventing the rotor from rotating relative to the rotor shaft. The rotor parts carry permanent magnets arranged with a fixed pitch angle over their outer peripheral faces. The rotor shaft has a single key for engaging with both an engagement groove of the first rotor and an engagement groove of the second rotor. The engagement groove of each steel plate forming the rotor parts is formed in a position shifted 1/2 of the skew angle from the pole center of a given one of the permanent magnets. The steel plates of the first rotor part and the steel plates of the second rotor part face in opposite directions when fitted to the key of the rotor shaft, thereby providing the predetermined skew angle between the two rotor parts.

What is claimed is: 
     
       1. A motor comprising: a rotor shaft;   a rotor axially divided into a plurality of rotor parts including at least first and second rotor parts, each of which is fitted on the rotor shaft in a manner that prevents rotation relative to the rotor shaft, and each of said rotor parts having circumferentially spaced magnet fittings, said magnet fittings holding a plurality of permanent magnets in respective circumferentially positions spaced to define a pitch angle therebetween; and   a stator disposed radially outward from the rotor,   said rotor shaft comprising engaging means extending axially of the rotor shaft for fitting into both a first engagement fitting of said first rotor part and a second engagement fitting of said second rotor part such that the first engagement fitting of said first rotor part aligns with the second engagement fitting of said second rotor part, said engagement fittings being radially aligned with said engaging means along a first radial line,   each of said first rotor part and said second rotor part comprising a laminate of a plurality of steel plates, each of the steel plates having a plate fitting, the plate fittings of the steel plates of said first and second rotor parts forming said first and second engagement fittings, respectively, the steel plates of said second rotor part being reversed on said rotor shaft relative to the steel plates of said first rotor part so that a center of a given one of said magnet fittings of said first rotor part, defined by position relative to said first engagement fitting, defines a second radial line at a predetermined angle +θ with said first radial line and a center of said given one of said magnet fittings of said second rotor part, in the same position relative to said second engagement fitting, defines a third radial line at a a predetermined angle -θ with said first radial line, θ being greater than 0 and less than P/2 where P is said pitch angle.   
     
     
       2. A motor according to the claim 1, wherein said predetermined angle θ is determined as follows: if 0<θ≦P/4,     θ={(n/2)+(1/4)}×S     if P/4<θ<P/2,     θ=(P/2)-{(n/2)+(1/4)}×S     where S is a slot pitch angle of the stator, and n is an integer.   
     
     
       3. A motor according to claim 1, wherein said predetermined angle θ is determined as follows: if 0<θ≦P/4,     θ={n+(n+(1/2)}×S     if P/4<θ<P/2,     θ=(P/2)-{n+(1/2)}×S     where S is a slot pitch angle of the stator, and n is an integer.